X-ray unit



1, 1940. A. MUTSCHELLER X-RAY UNIT Filed Nov. 19, 1938 30 IO l3 3b 4b IOb I N VEN TOR.

Patented Oct. 1, 1940 UNITED, STATES PATENT OFFICE 8 Claims.

This invention is an improvement in so-called shock-proof and stray-ray proof X-ray apparatus. By a novel arrangement of the component parts of an X-ray apparatus and by overcoming some difliculties which have such arrangements previously madeimpossible, I have discovered certain facts which are. herein described with the aid of the schematic diagrams of the draw ing and the description of a few examples.

Fig. 1 is a diagrammatic representation in section of such a unit to be connected to a high tension transformer. It shows some of the essential details, such as filament heating transformers, method of cooling the X-ray anode, etc.,

which details are not, shown in the other figures that follow'Fig. 1.

Fig. la is a simplified schematic representation of the electrical parts of Fig. l, and illustrates the circuit employed. It shows how high potential accumulates on the conducting parts which are connected to the electrodes of the X-ray tube and which are centrally located in the housing. This unit is energized by applying alternating current tothe condensers as shown while one electrode of each ofthe valve tubes are connected together via the grounded metal housing.

Fig. 2 is a similar arrangement, except that a different type of X-ray and valve tube is employed.

Fig. 3 shows how the conducting cables between the transformer and. the unit can be designed so that they function at the same time a condensers.

Fig. 4 is a diagram of a slightly different way of connecting the component units, and

Fig. 5 is a scheme in which the X-ray and the valve tube electrodes are housed in one envelope and in which only one high tension cable is employed.

It is well known, thatif one terminal of an alternating current source is applied to one of the electrodes of an electron discharge tube or valve tube and the other electrode of this valve tube is connected to one plate of a condenser while the second plateof the condenser is conconnected to the second terminal of the alternating current source, that then an Luiipolar charge accumulates or piles up on the condenser.

It is my discoveryQthat if these component parts of an X-ray apparatus together with an X-ray tube are built into a tank or housing which is X-rayopaque and electrically grounded, there arise highly valuable advantages and improvements in X-ray apparatus of the X-ray-proof and 1 the shock-proof type. These advantages arise out of the fact, that in this combination it is possible, for instance, to ground various electrical parts on tothe housing and this simplifies the construction and decreases the size I of the unit. Or it ispossible in some cases, to double the inlet Voltage from the transformer inside the unit through which the problem of insulating of high voltage carrying parts is very much simplified. In one of the possible forms only one cable supplying the high voltage to the unit is required and this cable also carries only one-half of the voltage applied to the electrodes of the X-ray tube.

These and many other advantages are the result of a certain grouping of the component parts in combination with anX-ray tube and an electrically grounded housing or shield of which several arrangements are described in the following. But in all these arrangements the basic principle is the same and even other similar or equivalent arrangements might be made.

Thus, in each of the five figures shownjif the transformer terminal I is negative, then the cathode 3 of the valve unit which is conductively connected to it and of which it is a part will pass electrons over to its anode 4. The condenser plate or electrode 5, which is connected to this anode 4, will then be charged to a negative potential toward the second plate or electrode 6, which is conductively connected to the other transformer terminal 2.

In Figs. 1, 2 and 3, the alternating current, before it applies to the valve unit cathode 3, first passes through a condenser l6; but it is well known in the art, that an alternating current can thus be transmitted and its magnitude depends on the frequency of the current and the size of the condenser. This condenser has another function which is explained further on. Also the two condensers of Figs. 4 and 5 are connected together in series via a grounded portion, generally the housing. In Figs. 2, 3 and 5, the electrodes of the X-ray tube and of the valve unit are placed into the same evacuated envelope but this is an expedient which does notalter the mode of functioning or the principle of action of the apparatus. If suitably guarded, the two sets of electrodes function without interference from each other and this double unit functions in the same way as the two sets of electrodes each mounted in a separate envelope.

In Fig. 1, an X-ray tube In is located between two plates ll and [2 of dielectric material each having in its center an opening to pass the tube terminals through and around which opening there is provided an elevation to form a collar I3 making insulative contact with the X-ray tube possible and thereby shielding the glass bulb against intensive electrical strain, The X-ray tube and the method of mounting these voltage barrier plates are preferably those in which parts having the envelope walls or dielectric voltage barriers placed along equipotential surfaces rather than along lines of force, thus avoiding a tendency to creepage and dielectric breakdown. But any of the customary types of X-ray tubes can also be employed to carry out the invention.

On the side of the dielectric plates opposite the X-ray tube, there are two valve tubes I4 and I5 and two condensers I6 and II. It is found convenient to construct these condensers by winding the flexible sheets of dielectric material together with the two conducting plates or foil of metal upon a tube of insulating material I8 and I9. Each of the two valve tubes can then be conveniently housed within one of these tubes.

One terminal of each of the valve tubes is connected to the oppositely poled terminal of the X-ray tube and the other terminal is connected to a common conductor or ground, such as the cover parts of the housing 20 and 2|. ,It is to be observed, that the inner conducting sheet of each of the condensers is connected to the conducting parts which connect the electrodes of the X-ray tube and of the valve tubes. For that reason, there is then. no difference of potential between the inner layer of the condenser, the inward electrodes of each of the valve tubes and the thereto connected X-ray tube electrodes; the outward electrodes of the valve tubes are grounded on to the housing. Each one of the two condensers and valve tubes are located in metallic housings 22 and 23 lined with dielectric material 24 and 25 and this housing may be filled with a dielectric medium such as oil, gas under pressure or other highly dielectric substances, or if sufficiently largein size, it may be filled with atmospheric air.

The two step-down transformers 26 and 2! are provided to heat the filaments of the valve tube I5 and of the X-ray tube I 0. These transformers are insulated for high voltage to prevent the high voltage piling up on the condensers from shortcircuiting into the primary supply lines. The two connecting wires to these transformers in the cables I and 2 carry primary heating current from insulated transformers and they serve also as conductors for the high tension current from the main transformer. The cathode of the valve tube I4, which is grounded, is heated by means of the low voltage current from wire 28 coming from a low voltage transformer having one of its legs grounded and one side of the filament also connected to ground such as the housing.

The channels 29 are for the circulating of a cooling medium through the X-ray tube anode. This medium may be oil, water or air and the object of it is to carry away from the anode the heat generated during the production of X-rays. The doors 20 and 2| are removable so as to make access to and removal of the valve tubes easily possible. When fastened, the doors are electrically grounded on to the remaining portion of the grounded metal housing. The two metal housing caps 22 and 23 fit on to the cylindrical metal section 30 which contains the X-ray tube and which is made of X-ray opaque material and provided with an exit window covered with a filter 3I to allow the useful X-rays to be emitted therethrough.

The operation of the unit is as follows: alternating current is applied to the primaries of the filament transformers 26, 21 and to the Wire supplying the filament 3 with low voltage heating current to properly heat the cathodes 3 and 32 to electron emission; the X-ray cathode 33 is heated to a smaller emission so that cathodes 3 and 32 function as valve tube cathodes operating below voltage saturation and so that cathode 33 functions as an X-ray producing cathode operating at voltage saturation.

We have then in Fig. 1 two groups of parts, the first group including the cathode 33 of the X-ray tube ID, the anode 4 of the valve tube I4 and one plate of the condenser I! which are connected together and which parts are located centrally and equispaced from the walls of the housing 23 as the result of which very good insulation of these parts for high tension current can easily be obtained; the second group is a rectifier means Which produces out of alternating current a unidirectional pulsating current, and a source of alternating current, comprising in this case, the condenser Hi, the valve tube I5 and the conductors I and 2 connected from a transformer to the condensers I6 and II.

The rectifier means shown in this Fig. 1, directs negative impulses from the conductor I through the condenser tubes I5 and I4 on to the cathode of the X-ray tube and leaves there a negative charge; a moment later, when the conductor I is positive, the impulse is directed to the anode of the X-ray tube and the conductor 2, which is then negative, adds another charge to that already piled up on the cathode of the X-ray tube.

Exactly the same process takes place at the anode of the X-ray tube and we have, therefore, high voltage equal to two charges piled up on the well insulated parts connected to the anode and the cathode of the X-ray tube which are centrally located and well insulated in the housing; all other parts carry a lower voltage, equal to either one charge or they are grounded on to the housing.

In Fig. 1a, the electrical parts of Fig. l which form the circuit are shown schematically and in simpler form to illustrate the circuit traced in the above paragraph.

The insulation of the cables I and 2, the condensers I6 and II, the filament heating transformers 26 and 21 and the valve tubes is therefore never required to be for more than onefourth the total voltage applied between the X-ray tube terminals except at the cathode of the valve tube I5, the X-ray anode 34, the X-ray cathode 33 and the valve tube anode 4 which are located in the middle portion of the unit and where they are therefore well insulated.

In Fig. 2, a novel type of combination of X-ray and valve tube electrodes placed in one envelope I0 is shown located between two plates II and I2 of dielectric material and on the other side of these plates and housed in metal shells are two condensers I 6 and I1. In this case the valve tube is incorporated in the X-ray tube and hence the condensers may be constructed as fiat discs of metallic conductors having plates of dielectric material sandwiched between. The borders of these insulating discs may project s-ufi'iciently far over the metallic plates to provide sufficient insulation for the conducting plates or there may be provided a lining for the metallic housing of I6, through the valve dielectric substance similar to that shown in connection with Fig. 1.

In Fig. 2 and Fig. 3 the first group of parts include the anode 4a, the X-ray cathode and theplate 5a of the condenser Ila; the second group or the rectifier means comprise the condenser Ilia, the valve tube cathode 3a and the conductors la and 2a leading to the transformer. EX- cept for differences of construction of these parts, the result and the principle of action is exactly the same as that of Fig. 1.

, Still another variation of the inventive idea is shown in Fig. 3. Here the same type of tube It! is shown as in Fig. 2; but the condensers l6 and I! are shown as part of the cables which connect the unit with the high tension transformer. Instead of providing ordinary insulated conducting cables through which the current impulses are delivered to the condenser, the cable is developed as a condenser having one conductor in the form of a central conductor connected to the X-ray tube and being surrounded with insulating material it has a second tubular layer of conducting material which is connected to one transformer terminal. It is generally again covered with insulating substance and a grounded metallic covering. In this manner, the cable serves a twofold purpose, that of a condenser and that of a conductor if alternating current is applied to it. In this arrangement dielectric plates may be used on either side of the X-ray tube as in Figs. 1 and 2, or there may be provided a sufficiently large air space to produce the required insulation for the conductors. from the condensers to the vacuum tube.

In the devices illustrated in Figs. 1, 2 and 3, through the fact that a potential is piled up on one of the condensers through a valve tube, advantage is taken of the resulting doubling of the voltage in the grounded housing containing the X-ray tube while alternating current is being fed in through a condenser. With the same arrangement of these parts, still another advantage can be gained which is illustrated in Fig. 4 and Fi 5.

In Fig. 4, in an arrangement similar to that described in connection with Fig. 1, there is also an X-ray tube. Ill sandwiched in between two plates 1 l and [2 of dielectric substance. These plates have each a hole in its center and a collar to enable obtaining dielectric contact'with the envelope of the X-ray tube near the seal-in place for the electrodes. On each of the other sides of the plates are again located a condenser wound on a tube of dielectric substance and a valve tube located in. its center. But one of the plates of the condenser is connected to one of the X-ray tube electrodes and the oppositely poled valve tube electrode; the other is grounded on to the housing and the alternating high voltage current is applied to the outwardly pointing terminal of each valve tube. Therefore, since theouter plate of the condenser is grounded on to the housing, it is not required that a lining of insulating material be provided to insulate the condenser.

The electrical performance of the unit is the same as that of Fig. 1. The cathode of the X-ray tube We, the anode 4c of the valve tube 30 and one plate of the condenser IBc are connected together and are centrally located with respect to the housing. The rectifier means consist of the valve tube 30 which passes impulses of one polarity but which blocks those of opposite polarity and thus passes rectified current on to the oathode of the X-ray tube. The same action, in the form or constant potential discharge is small and the rate of charging during the impulses is relatively large. Hence, if the capacity of the condensers is large and the frequency of the alternating current is high, then the current discharging through the X-ray tube is approaching uniform or constant potential.

' Through the use of a novel type of X-ray tube having additional electrodes, still another simplification illustrated in Fig. 5 becomes possible. These auxiliary discharge electrodes 3 and 35 operating below voltage saturation are connected to one terminal of a transformer l, of which the other terminal is grounded. The alternating impulses are then directed either to one or the other of the two electrodes 4 or 32 which are connected to theanode and the cathode of the X-ray tube, depending on the polarity. The condensers l6 and I! are located on each side on the outside of the dielectric plates H and [2 between which the X-ray tube is located. The terminals of the X-ray tube or the members supporting the X-ray tube are sov constructed as to be a part of one of the plates of the condenser or so as at least to be connected to it, and the other or second plate is grounded on to the housing. Thus, if the inlet cable I supplies high tension alternating current, it will distribute its impulses alternately to the right and to the left according to the polarity of the impulse and so on each of the two condensers l6 and I1, there will accumulate a charge which can not leak over or off the auxiliary electrodes, but which can discharge only over the X-ray electrodes.

Thus in this figure again, the cathode of the X-ray tube, the anode 4d of the valve tube which are housed in the one evacuated envelope and the plate 511 of the condenser Hid are connectedtogether and are centrally located in the housing. The rectifier means comprise the cathode 4d and the anode 35d which are energized with alternating current from the cable 205, supplying rectified current to the cathode of the X-ray tube as in the case of the other figures and the possibility of being able to use but one high tension conducting cable, affords some further valuable simplifications.

Having thus described and illustrated with schematic drawing several examples of the application of my invention, I do not limit myself to these specific forms but I claim the broad idea illustrated therein.

I claim:

1. A stray-ray-proof and shock-proof X-ray unit comprising a housing of X-ray opaque material provided with an exit portion for X-rays, X-ray generating electrodes and valve action electrodes, evacuated envelope means of high dielectric material in which the electrodes are supported, a condenser, one terminal of said X-ray generating electrodes, an oppositely poled terminal of said valve action electrodes and one terminal of said condenser being connected together, said terminals being located centrally and substantially equispaced from the walls of said housing whereby good insulation of said terminals for high voltage is obtained, and means for supplying high voltage current to said interconnected terminals and to the second terminal of said X-ray generating electrodes, whereby a unipolar charge is piled up on said interconnected terminals.

2. A stray-ray-p-roof and shock-proof X-ray unit as recited in claim 1, in which the X-ray generating electrodes and valve action electrodes are mounted in a single evacuated envelope.

3. A stray-ray-proof and shock-proof X-ray unit as recited in claim 1, in which the X-ray generating and the valve action electrodes are supported in different evacuated envelopes.

4. An X-ray unit of the shock-proof and rayproof type comprising a housing of X-ray nontransparent material provided with an outlet portion for X-rays, X-ray generating electrodes and valve action electrodes, evacuated envelope means of high insulative properties in which the electrodes are supported, a condenser, the cathode terminal of said X-ray generating electrodes, the anode terminal of said valve action electrodes and one terminal of said condenser connected together and centrally located from the walls of said housing whereby good insulating conditions for said terminals for high voltage is obtained, and means for supplying high voltage current to said interconnected terminals and to the anode of said X-ray generating electrodes, whereby a unipolar charge is piled up on said interconnected terminals.

5. An X-ray unit as recited in claim 1 in which the said condenser is developed as concentric flexible conductors spaced with flexible dielectric in the form of a flexible high insulating cable.

6. An X-ray unit of the shock-proof and rayproof type having a housing of X-ray opaque material provided with an X-ray transparent portion in the form of a cylinder closed with rounded ends, an X-ray tube, a valve tube and a condenser contained in said housing, one electrode terminal of said X-ray tube and an unlikepoled terminal of said valve tube and one plate of said condenser connected together and located substantially centrally in one portion of said housing and in another portion of said housing a valve tube and a condenser for rectifying alternating current and applying impulses thereof to the properly poled terminals of said X-ray tube.

7. An X-ray unit of the shock-proof and rayproof type comprising a housing of X-ray nontransparent material provided with an outlet portion for X-rays, X-ray generating electrodes and valve action electrodes, evacuated envelope means of high insulative properties in which the electrodes are supported, a condenser, the anode terminal of said X-ray generating electrodes, the cathode terminal of said valve action electrodes and one terminal of said condenser connected together and centrally located from the walls of said housing whereby good insulating conditions for said terminals for high voltage is obtained, and means for supplying high voltage current to said interconnected terminals and to said cathode of said X-ray generating electrodes, whereby a unipolar charge is piled up on said interconnected terminals.

8. An X-ray unit of the shock-proof and rayproof type comprising a housing in the form of a cylinder and having an outlet for X-rays and rounded ends of X-ray opaque material, located in one rounded portion a rectifier means comprising a valve tube and a condenser and in the cylindrical portion an X-ray tube, a wall of dielectric substance between said X-ray tube and said condenser having an opening centrally located therein and one electrode terminal of said X-ray tube passing through said opening and said terminal connected to an oppositely poled electrode terminal of said valve tube and to one plate of said condenser, in the second rounded portion of said housing located a second rectifier means comprising a valve tube and a condenser, a second wall of dielectric substance between said X-ray tube and said condenser having an opening centrally located therein and one electrode terminal of said X-ray tube passing through said opening and said terminal connected to an oppositely poled electrode terminal of said valve tube and one plate of said condenser and means for energizing said rectifier means whereby properly poled impulses are applied to the electrode terminals of said X-ray tube.

ARTHUR MUTSCHELLER. 

